Television sets on sale at a John Lewis store. The retailer said smart TVs were proving particularly popular, with sales up 40% in the past two weeks. Photograph: Frank Baron for the Guardian

John Lewis has seen a boom in television sales as Britons prepare to watch the World Cup, starting on 12 June.

Sales of televisions soared 47% in the week to 31 May, compared with the same week a year before. School half-terms and wet weather over the bank holiday also helped John Lewis pull in more shoppers, lifting total sales by 17%, the retailer's strongest performance in more than three months.

John Lewis said smart TVs were proving particularly popular, with sales up 40% in the past two weeks, while curved TVs were also attracting attention.

Howard Archer, chief UK and European economist at IHS Global Insight, said retailers were likely to see a boost in spending as shoppers snapped up replica kits and souvenirs, food and drink to eat while watching the tournament from their sofas, as well as the new televisions.

"The better England do and the more games they play, the bigger the potential beneficial impact to retail sales. And if England do well, it could give a small, temporary boost to consumer confidence," Archer said.

Nearly 70% more replica shirts were sold in the three months to July 2010, the time of the last World Cup, hitting a total value of £42.4m, 86% more than a year before as prices were also increased.

British stores were expected to sell an additional 170,000 televisions between late April and the beginning of the tournament, worth around £70m more than would usually be expected, according to research by industry analysts GfK. It said sound bars, which boost television speaker quality, were also likely to sell well.

However, GfK said the sales of televisions would merely bring forward purchases that were already being planned by fans and would not boost the market for this year overall.

Meanwhile, some of the money expected to be spent on World Cup-related goods would be diverted from other potential purchases. In addition, if England were to crash out in the group stage, there would likely be piles of England paraphernalia in bargain bins.